linux-kernel - Re: [PATCH v3 5/6] x86/ftrace: Use text

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Message-ID: <nycvar.YFH.7.76.2001290141140.31058@cbobk.fhfr.pm>
Date:   Wed, 29 Jan 2020 01:46:55 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Jessica Yu <jeyu@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, live-patching@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()

On Tue, 28 Jan 2020, Josh Poimboeuf wrote:

> > Anyway, I think that we might make your life easier with using the 
> > proposed -Wsuggest-attribute=noreturn.
> 
> Maybe.  Though if I understand correctly, this doesn't help for any of 
> the new warnings because they're for static functions, and this only 
> warns about global functions.

Could you please provide a pointer where those have been 
reported/analyzed?

For the cases I've seen so far, it has always been gcc deciding under 
certain circumstances not to propagate __attribute__((__noreturn__)) from 
callee to caller even in the cases when caller unconditionally called 
callee.

AFAIU, the behavior is (and always will) be dependent on the state of gcc 
optimizations, and therefore I don't see any other way than adding 
__noreturn anotation transitively everywhere in order to silence objtool.

So those cases have to be fixed anyway.

What are the other cases please? Either I have completely missed those, or 
they haven't been mentioned in this thread.

Thanks,

-- 
Jiri Kosina
SUSE Labs